Water scavenging system

Abstract

A method of removing water ( 7 ) from a fuel tank ( 2 ) using a water scavenging line ( 4 ) which has an inlet ( 6 ) immersed in the water and an outlet ( 5 ) coupled to a water tank ( 3 ). The method comprises filling the fuel tank with fuel ( 30 ) whereby the fuel exerts hydrostatic pressure on the water, the hydrostatic pressure driving the water up the water scavengingline against the force of gravity and into the water tank. The use of hydrostatic pressure provides an automatic and relatively simple method of extracting the water from the bottom of the fuel tank. The water tank enables the extracted water to be stored for disposal at a later time, typically by feeding the water into an engine.

The invention claimed is: 
     
       1. A method of removing water from a fuel tank using a water scavenging line which has an inlet immersed in the water and an outlet coupled to a water tank, the method comprising the steps of:
 filling the fuel tank with fuel whereby the fuel exerts hydrostatic pressure on the water, the hydrostatic pressure driving the water up the water scavenging line against the force of gravity and into the water tank; and 
 feeding water from the water tank through a water output line and into an engine. 
 
     
     
       2. The method of  claim 1  further comprising using hydrostatic pressure to feed the water from the water tank into an engine fuel line. 
     
     
       3. The method of  claim 1  wherein the fuel tank is an aircraft fuel tank. 
     
     
       4. The method of  claim 3  further comprising opening a valve in the water output line in response to an increase in an effective pitch of the aircraft. 
     
     
       5. The method of  claim 3  further comprising opening a valve in the output line in response to a decrease in an effective pitch of the aircraft. 
     
     
       6. A water scavenging system for removing water from a fuel tank, the water scavenging system comprising:
 a water tank; 
 a water scavenging line which has an outlet coupled to the water tank, 
 
       wherein the water scavenging line has an inlet which is immersed in water at a bottom of the fuel tank at a level below the outlet of the water scavenging line, whereby hydrostatic pressure can drive the water up the water scavenging line against the force of gravity and into the water tank; and
 a water output line which has an inlet coupled to the water tank, and an outlet which is coupled to an engine fuel line. 
 
     
     
       7. The system of  claim 6  further comprising a non-return valve in the water scavenging line. 
     
     
       8. The system of  claim 6  wherein the outlet of the water scavenging line is positioned higher than the lowest point of the water tank. 
     
     
       9. The system of  claim 8  wherein a portion of the water scavenging line extends through a wall of the water tank. 
     
     
       10. The system of  claim 8  wherein the outlet of the water scavenging line comprises a guide directed towards the bottom of the water tank. 
     
     
       11. The system of  claim 6  further comprising a valve in the water output line. 
     
     
       12. The system of  claim 11  wherein the valve in the water output line is configured to open and close in response to a change in an effective angle of the valve. 
     
     
       13. The system of  claim 12  wherein the valve has a closed configuration in which the valve impedes the flow of water in the water output line; and positive and negative open configurations in which the valve permits water to flow through the valve, wherein the valve is configured to change from its closed configuration to its positive open configuration in response to an increase in effective angle of the valve; and wherein the valve is configured to change from its closed configuration to its negative open configuration in response to a decrease in effective angle of the valve. 
     
     
       14. The system of  claim 6  configured to remove water from an aircraft fuel tank, wherein the inlet of the water output line is offset towards the rear of the water tank relative to the direction of travel of the aircraft. 
     
     
       15. The system of  claim 14  wherein the inlet of the water output line is positioned higher than the lowest point of the water tank. 
     
     
       16. The system of  claim 14  further comprising a non-return valve in the water output line. 
     
     
       17. The system of  claim 6  configured to remove water from an aircraft fuel tank, wherein the outlet of the water scavenging line is offset towards the front of the water tank relative to the direction of travel of the aircraft. 
     
     
       18. The system of  claim 6  configured to remove water from an aircraft fuel tank, wherein the outlet of the water scavenging line is positioned forward of the inlet of the water output line relative to the direction of travel of the aircraft. 
     
     
       19. The system of  claim 6  wherein the water tank has an opening at its top which can permit fuel to flow into the water tank. 
     
     
       20. The system of  claim 6  wherein the inverse aspect ratio of the water tank is greater than 2. 
     
     
       21. The system of  claim 20  wherein the inverse aspect ratio of the water tank is greater than 4. 
     
     
       22. A fuel tank system comprising:
 a fuel tank; and 
 a water scavenging system according to  claim 6 , installed with the inlet of the water scavenging line immersed in water at a bottom of the fuel tank and the outlet of the water scavenging line coupled to the water tank above the inlet, whereby hydrostatic pressure drives the water up the water scavenging line against the force of gravity and into the water tank. 
 
     
     
       23. The system of  claim 22  further comprising an engine fuel line coupled in parallel to the water tank and the fuel tank. 
     
     
       24. The system of  claim 22  further comprising a pump coupled in parallel to the water tank and the fuel tank. 
     
     
       25. The system of  claim 22  wherein the fuel tank is an aircraft fuel tank. 
     
     
       26. The system of  claim 22 , wherein the water tank has a capacity which is less than 1% of the capacity of the fuel tank. 
     
     
       27. The system of  claim 26 , wherein the water tank has a capacity which is less than 0.1% of the capacity of the fuel tank.